Traditional paper-making systems include the provision of a water-based slurry, termed a "paper furnish", containing wood fibers, fines, and other ingredients to a moving web on a paper machine to facilitate the formation of a paper matrix, which is drained, dried and pressed into a final paper sheet product. A desire in such a process is to drain the excess water in an efficient manner to form a heterogeneous matrix without also unnecessarily removing desired fibers, fines and other solids. Retained undesired water burdens the downstream processes, such as, for example, a wet sheet in the dryer section. However, removal of desired solids endangers acceptability of the final paper sheet. Also, the act of draining water can adversely affect sheet formation.
Retention aid systems have been developed to increase retention of desired fibers, fines and solids, to improve paper sheet formation, and to drain better the paper matrix in the paper sheet forming section of paper machines. Such systems benefit, in part, the papermaker by allowing the paper machine to run more cleanly while producing a better sheet at higher machine speeds. Among the retention aid systems are those which utilize natural and synthetic microparticle systems. Certain of these retention aids include colloidal aluminum hydroxide, colloidal magnesium silicate, bentonite, colloidal silica, and organic polymer based systems.
Depending upon cost, quality, customer requirements and other considerations, the papermaker may employ a number of differing strategies of retention aid use. One typical strategy is to add an agglomerating agent to a thin stock precursor to the paper furnish. Such agent acts to agglomerate or flocculate the fibers, fines and solids. Typical agents are starch and/or polymers. However, such systems often subsequently subject the agglomerated material to a shearing force in screening equipment to produce smaller agglomerates with an intended purpose to obtain better sheet formation. A retention aid to help retain the fiber, fines and other desired solids can be added to the system before the furnish is passed through the paper machine head box to begin the paper matrix formation on the paper machine web. This retention aid causes a second agglomeration differing from the previous agglomeration.
Such aids have varying degrees of effectiveness due to the numerous variables in the paper-making process. One strategy is to formulate in a remote production facility various aids having a variety of relative percentages of the components. These differing percentages in the retention aid's composition are intended to match the requirements of the furnish for overall system performance. Such strategy often makes performance a result of art and happenstance rather than of engineered control. What are needed are better drainage aids and retention aids and methods of using such aids in the paper-making process.
Further, a system of agglomerating particles is sometimes useful in the treatment of water in trapping or otherwise removing undesired particles and oils or other globules from water. While many systems for water treatment exist based upon agglomeration principles, new and useful agglomerants are still desirable.
Accordingly, it is an object of the present invention to provide synthetic mineral microparticles, specifically metallic microparticles, which are new to the paper-making art and which provide equal or enhanced performance compared to present retention and drainage aids. It is a further object to provide a method for the production of such synthetic mineral microparticles.
Another object is to use the synthetic mineral microparticles in a novel method of production in paper-making systems by providing such particles as drainage and retention aids. In another aspect of the present invention, it is an object to provide a system of agglomeration useful in water treatment.